Nondestructive inspection (NDI) of a structure involves thoroughly examining the structure without harming it or significantly disassembling it. Nondestructive inspection is commonly used in the aircraft industry to validate the health (e.g., integrity and fitness) of aircraft structures.
An ultrasonic probe may be used to perform NDI of a structure. A conventional probe typically includes a transducer having an array of elements that direct acoustic signals toward the structure and measure reflections of the signals.
An acoustic coupling fluid is used to propagate the acoustic signals between the probe and a structure under inspection. During inspection, a surface of the structure may be wetted with an acoustic coupling fluid such as water.
Edge related problems are experienced by an array losing coupling off the edge of a structure under inspection. As a probe is moved off the edge, the particular array element that is located off the structure's edge will lose coupling. If coupling between the probe and the structure is lost, acoustic signals will not be propagated from and to that array element. Consequently, reflected signals will not identify edges of the structure under inspection.
It would be desirable to maintain coupling over edges of structures during NDI with an ultrasonic probe.